Gut microbiota, metabolic syndrome, obesity and the nutrient sensor pathways Department of Gastroenterology, Endocrinology & Metabolism Medical University Innsbruck Herbert Tilg Nothing to disclose
Fig. 1 The gut microbiota in development and disease.? Nicholson et al. Science 2012;336:1262-1267
Overview Microbiota regulates hepatic steatosis Innate immunity critically involved: TLRs, inflammasome Hepatic steatosis/metabolic dysfunction: transmissible via the microbiota Nutrient sensor pathways Conclusions
Link microbiota and NAFLDrelated immune dysfunction Ob/ob mouse has intestinal stasis Cope et al., Gastro, 1999 Intestinal bacterial overgrowth Endogenous ethanol production Damaged GI epithelial barrier Permit EtOH/LPS escape? Induce inflammatory cytokines?
Role of small intestinal bacterial overgrowth in NASH (Gut 2001) 22 patients with NASH studied ( 14 C-D- Xylose and lactulose breath test) Higher prevalence of bacterial overgrowth in patients with NASH compared to controls In parallel, NASH patients demonstrated higher circulating TNF-α levels (no increase in circulating endotoxin)
Probiotics and anti-tnf improve NASH ob/ob ob/ob + VSL#3 ALT ALT Li et al. Hepatology 2003
Gut microbiota regulates fat storage Bäckhed F et al. PNAS 2004 Three groups of mice: -germ-free state -Those allowed to acquire a microbiota from birth to adulthood (CONV-R) -Raised GF until adulthood and then colonized for 2 weeks with an unfractionated cecal microbiota from CONV-R donors (CONV-D)
Gut microbiota regulates fat storage Bäckhed F et al. PNAS 2004 A 14-d conventionalization of WT GF mice increases circulating leptin levels and decreases sensitivity to insulin (A) Leptin, insulin, glucose levels; (B) Glucose tolerance, (C) Insulin tolerance
Gut microbiota regulates fat storage Bäckhed F et al. PNAS 2004 Conventionalization induces hepatic lipogenesis and nuclear import of the basic helix-loop-helix transcription factor (ChREBP) A) Hepatic oil-red staining B) Liver TG levels C) qrt-pcr assays of liver mrnas D) IH studies
Gut microbiota regulates fat storage Bäckhed F et al. PNAS 2004 Fasting-induced adipocyte factor (Fiaf) Conventionalization promotes adipocyte hypertrophy by suppressing Fiaf expression in the intestine: A) epidydimal fat pads, B) qrt-pcr assays of epidydimal mrnas, C) LPL activity, D) Fiaf expression, E) generation of a fiaf -/- mouse, F) absence of Fiaf markedly attenuates the increase in total body fat content after a 14-d conventionalization
Gut microbiota regulates fat storage Bäckhed F et al. PNAS 2004 Processing of dietary polysaccharides Increased hepatic lipogenesis (ChREBP/SREBP-1) Microbial colonization of the gut Suppression of Fiaf in the gut epithelium LPL activity Triglyceride storage in adipocytes and liver LINK: Gut microbiota energy harvest energy storage HEPATIC STEATOSIS
Mechanisms underlying the resistance to diet-induced obesity in germ-free mice Bäckhed F et al. PNAS 2007 GF mice are protected against diet-induced obesity Gut microbiota suppresses AMPK activity ( fuel gauge that monitors cellular energy status)
Potential interactions of the microbiota with metabolic (liver) pathways Tilg H. Gastroenterology 2009
Evolution of Steatosis/Metabolic Syndrome: A role for other factors? Gut Microbiota? Cytokines? Innate immunity? Inflammasome?
TLR5 KO mice develop obesity (Vijay-Kumar et al. Science 2010) M Vijay-Kumar et al. Science 2010;328:228-231 Fig. 1 T5KO mice develop obesity.
TLR5 KO mice exhibit insulin resistance M Vijay-Kumar et al. Science 2010;328:228-231 Fig. 2 T5KO exhibit hyperglycemia/insulin resistance.
Disease transfer via gut microbiota A-C: Antibiotic therapy D-H: 4 week old GF WT mice received intragastrically cecal content from WT or T5KO mice M Vijay-Kumar et al. Science 2010;328:228-231 Fig. 4 T5KO gut microbiota is necessary and sufficient to transfer metabolic syndrome phenotype to germ-free mice.
Role of TLR5 challenged? Letran SE et al. J Immunol 2011; 186:5406 2 different colonies with TLR5-deficiency studied Intestinal inflammatory disease and metabolic dysfunction not evident Only observed an impaired CD4 T cell response to flagellated pathogens differences in the gut microbiota between institutional animal facilities or differences obtained during rederivation of these animals might explain divergent phenotypes
Liver toxicity is mediated via TLR9 and Nalp3 inflammasome J Clin Invest 2009 ASC (apoptosis associated speck-like protein containing CARD) Inflammasome consists of an NLR (nucleotide-binding domain, leucinerich repeat-containing), ASC and caspase 1
Increased severity of NASH in inflammasome-deficient mice J Henao-Mejia et al. Nature 2012
Increased severity of NASH in Asc- and Il18-deficient mice is transmissible to co-housed wild-type animals DISEASE TRANSFER! J Henao-Mejia et al. Nature 2012
Increased severity of NASH in Asc-deficient and co-housed wild-type animals is mediated by TLR4, TLR9 and TNF-α J Henao-Mejia et al. Nature 2012
d) Glucose e) Insulin levels f) i.p. glucose challenge after 11 weeks of HFD 3 weeks of antibiotic therapy before 12 weeks of HFD
Inflammasome-deficiency-associated changes in the microbiota lead to hepatic steatosis and inflammation through input of TLR4 and TLR9 agonists leading to enhanced TNF liver expression Co-housing leads to disease in WT mice Relationship between microbiota, metabolic and auto-inflammatory (liver) disease
Dysbiosis and NASH: identification of the disease-modifying microbiota? (Henao-Mejia et al, Nature 2012) Antibiotic therapy (Cipro + Metro) significantly reduced the severity of NASH in Asc -/- mice, and abolished transmission of the phenotype to WT animals Significant increase in the family of Porphyromonadaceae Porphyromonas has been associated with several components of MS both in mice and humans, including atherosclerosis and T2DM Expansion of this taxa is strongly associated with complications of chronic liver disease
Metagenome-wide association study (MGWAS) 345 chinese subjects 60.000 type-2 diabetes-associated markers identified
Identification of T2D-associated markers from gut metagenome. No significant relationship between enterotype and T2D JJ Qin et al. Nature 2012. doi:10.1038/nature11450
Taxonomic and functional characterization of gut microbiota in T2D. MLGs, Metagenomic linkage group Red text = Enriched functions Blue text = Decreased functions
Gut microbiota of T2D patients show a moderate degree of dysbiosis 3,2 +/- 0.2% of gut microbial genes are associated with T2D in an individual JJ Qin et al. Nature 2012 doi:10.1038/nature11450
Early life treatment with vancomycin propagtes Akkermansia muciniphila and reduces diabetes incidence in the NOD mouse Adult mice treated from week 8 of age until development of diabetes Hansen et al. Diabetologia 2012
Early life treatment with vancomycin propagtes Akkermansia muciniphila and reduces diabetes incidence in the NOD mouse Insulitis score and blood glucose levels significantly lower in the adult group Vancomycin treatment decreased many major genera of Gram-positive and negative microbes while Akkermansia muciniphila became dominant Protective role for Akkermansia? Hansen et al. Diabetologia 2012
Gut microbiome and pregnancy Koren et al. Cell 2012 Many immune and metabolic changes occur during normal pregnancy 91 pregnant women of varying pregnancy BMIs and gestational diabetes status and infants studied
Gut microbiome and pregnancy Koren et al. Cell 2012 Gut microbiota changed dramatically between first (T1) and third (T3) trimesters Vast expansion of diversity between mothers and an overall increase in Proteobacteria and Actinobacteria T3 stool showed strongest signs of inflammation and energy loss When transferred to GF mice, T3 microbiota induced greater adiposity and insulin sensitivity compared to T1
Figure 1. 16S rrna Gene Surveys Reveal Changes to Microbial Diversity during Pregnancy. Microbial communities clustered using PCoA of the weighted UniFrac matrix. Cell Volume 150, Issue 3 2012 470-480
Figure 4 High Between-Individual Microbial Diversity in T3 Persists in the Women Postpartum and Is Observed in Their Neonates (A) Mean weighted (SEM) UniFrac distances between bacterial communities of women (sampled at T1, T3, and 1 month postp.
Koren et al. Host Remodeling of the Gut Microbiome and Metabolic Changes during Pregnancy Cell 2012, 150: 470-480
Nutrient sensor pathways link to metabolic inflammation Genetic Predisposition Gut Microbiota Dietary Factors Pro-inflammatory? Anti-inflammatory Metabolic syndrome, diabetes
Diet & Intestinal Immunity Tilg H. N Engl J Med 2012
Phosphatidylcholine - Atherosclerosis Pro-inflammatory diet Phosphatidylcholine (enriched in eggs, liver, meat etc) Drives inflammation concept of pro-inflammatory diets!! Wang et al, Nature 2011
Metabolism/NASH: Host and microbes in a pickle TLR4 TLR9 Products of gut microbiota such as SCFA, peptidoglycan or LPS activate different receptors of innate immune cells
Multiple parallel HITs Hypothesis 1st hits: Nutritional aspects Overweight Inflammation? Microbiota? Normal 1 st hit Inflammation Microbiota Steatosis/MS 2nd hits: Diet? Mediators? Innate immunity? Microbiota? Extrahepatic cytokine sources? Diabetes/Steatohepatitis Cirrhosis 2 nd hit 3 rd hit
Conclusions: Gut microbiota and obesity/diabetes Gut microbiota considered key factor regulating hepatic steatosis, MS and diabetes Diet: key environmental factor modulating gut s microbiota Involved mechanisms: TLRs, Fiaf, AMPK, ChREBP, cytokines, inflammasomes, ER stress
Conclusions Obesity, Metabolic Syndrome and NAFLD: is the cause in the GI Tract? May at least play an important role Microbiota, cytokines and inflammasome as major players including as therapeutical targets